1. Field of the Invention
The present invention relates to a method for forming a tire reinforcing layer, such as a carcass ply or a belt ply, either directly or indirectly on the outer circumferential surface of rubber member that is supported on a rigid core having a toroidal shape, and also to an apparatus which can be suitably used for carrying out the method.
2. Description of the Related Art
Conventional system for forming a tire reinforcing layer on a rigid core is disclosed, for example, in U.S. Pat. No. 5,281,289. In such a system, an installation head supports a reinforcing material in the form of a single cord, and is moved toward one side of a crown portion of the core which is under a slow rotation. With the leading end of the reinforcing material gripped and held by a clip, the installation head is moved in a diagonal direction from one side to the other of the core along the surface of the crown portion. Thus, the reinforcing material fed through the installation head is applied to the surface of the crown portion of the rubber member, with a predetermined inclination angle relative to the equatorial line of the core. Subsequently, the reinforcing material is cut by a cutter, at a position which is spaced a predetermined distance from the leading end. These process steps are repeated so that the reinforcing materials are joined to the outer circumferential surface of the rubber member one after another and in parallel with each other, thereby forming a tire belt layer on the core.
Since the reinforcing material to be applied to the outer circumferential surface of the rubber member is comprised of a single cord as explained above, it is necessary to perform the joining operation of the reinforcing material for a number of times in order to form a complete reinforcing belt layer. Therefore, with the known system, it has been difficult to realize improved work efficiency and productivity.
Furthermore, the application of the reinforcing material is performed by moving the installation head in the longitudinal direction of the reinforcing material. Thus, there is another problem that, when the inclination angle of the reinforcing material relative to the equatorial line of the core is small and the reinforcing material has a large length, it is necessary to move the installation head over a relatively long distance, i.e., a distance equal to the length of the reinforcing material. This makes it further difficult to achieve an efficient formation of a reinforcing layer with an improved productivity.
In view of the above-mentioned problems of the conventional system, it is a primary object of the present invention to provide improved method and apparatus for forming a tire reinforcing layer either directly or indirectly on the outer circumferential surface of a rigid core with higher efficiency and improved productivity.
According to one aspect of the present invention, there is provided a method for forming a tire reinforcing layer, wherein a continuous strip of a reinforcing material comprised of a plurality of single cords or twisted cords is cut into reinforcing elements having a predetermined length, and the reinforcing elements are each joined onto an entire outer circumferential surface of a rubber member on a rigid core having a toroidal shape, which is being subjected to an indexing movement about its center axis. The reinforcing elements are successively fed onto the outer circumferential surface of the rubber member from its one side, synchronously with the indexing motion of the core, and are then urged against the outer circumferential surface of the rubber member along their longitudinal direction and thereby successively pressure-joined to the rubber member.
With the above-mentioned method according to the present invention, it is possible to form a tire reinforcing layer, such as a belt layer, on the outer circumferential surface at the crown portion of a carcass, with higher efficiency and improved productivity as compared to the conventional system. This is because a plurality of cords are simultaneously pressure-joined to the outer circumferential surface of the rubber member on the rigid core. Furthermore, the reinforcing elements are urged against, and thereby tightly pressure-joined to the outer circumferential surface of the rubber member over the entire length thereof, e.g., by the urging operation of a pressure roll. It is thus possible to achieve a significantly improved joining of the reinforcing element to the rubber member while simultaneously avoiding entrapment of air therebetween. The entrapment of air can be more effectively prevented by pressure-joining the reinforcing element to the outer circumferential surface of the rubber member progressively from the leading end to the trailing end thereof.
Furthermore, according to the present invention, the joining of the respective reinforcing elements to the outer circumferential surface of the rubber member is performed based on a rotational movement of the core itself. Thus, by suitably selecting the rotational speed of the core, the joining of the reinforcing element can be performed within a minimized time even when the angle defined between the equatorial line of the core and the reinforcing element is small and the reinforcing element is relatively long. Therefore, the work efficiency of joining the reinforcing element can be advantageously improved, in contrast to the conventional system in which an installation head forming part of the mechanism is reciprocated.
With the method according to the present invention, the reinforcing element to be pressure-joined may be set at a predetermined inclination angle with reference to the equatorial line of the core, as a result of inclination of the center axis of the core by a predetermined angle within a vertical plane including the axis. It is however preferred that the setting of the inclination angle of the reinforcing element is performed by gradually changing the joining position of the reinforcing element relative to the outer circumferential surface of the rubber member in the longitudinal direction of the reinforcing element and in the width direction of the core, by displacing the reinforcing element in the axial direction of the core while rotating the core. In the latter case, the inclination angle of the reinforcing element relative to the equatorial line of the core can be readily set over a wide range and in a precise manner, without any particular operations, simply by suitably selecting the rotational speed of the core and the feeding speed of the reinforcing element.
Furthermore, according to the present invention, the side edges of adjacent reinforcing elements may be successively joined to each other on the circumferential surface of the rubber member. In this instance, it is preferred that the indexing movement of the core is performed by a normal rotation of the core for joining the reinforcing element to the rubber member, in combination with a reverse rotation of the core for returning the core to a starting position for joining a next reinforcing element.
Alternatively, the reinforcing elements may arranged on the outer circumferential surface of the rubber member on the core, while leaving a gap between opposite side edges corresponding to at least one sheet of the reinforcing element between the respective reinforcing elements, so that another reinforcing element can be arranged at the region of the rubber member corresponding to the gap. In this instance, it is preferred that the indexing operation of the core also serves as a normal rotation for joining the reinforcing element to the rubber member, such that the respective reinforcing elements are pressure-joined, at a first turn of the core, to the outer circumferential surface of the rubber member so as to leave the gap therebetween, and the successive reinforcing elements are pressure-joined to the region of the rubber member corresponding to the gap at the second and subsequent turns of the core.
In either case, it is preferred that the reinforcing element is pressure-joined to the outer circumferential surface of the rubber member by a pressure roll which is adapted to roll over the reinforcing element from its one end to the other. Such a pressure roll ensures that the reinforcing member in its entirety can be pressure-joined to the outer circumferential surface of the rubber member smoothly, uniformly and sufficiently tightly.
According to another aspect of the present invention, there is provided an apparatus for forming a tire reinforcing layer, comprising: a rigid core having an outer circumferential surface with a predetermined width, for supporting a rubber member thereon and adapted to be rotated about its center axis in normal and reverse directions; reinforcing element feed means for feeding a reinforcing element obtained by cutting a continuous strip of reinforcing material into a predetermined-length, from a predetermined feed direction onto an outer surface of the rubber member on the core; pressure-joining means for urging the reinforcing element against the outer circumferential surface of the rubber member and thereby pressure-joining the reinforcing element to the rubber member over the entire length of the reinforcing element; and lateral travel means for integrally displacing the feed means and the pressure-joining means in an axial direction of the core.
With the apparatus according to the present invention, the reinforcing element is fed to the outer circumferential surface of the rubber member by the reinforcing element feed means while the core is rotated at a predetermined speed in normal direction about the horizontal enter axis of the core. Simultaneously, the reinforcing element is progressively urged against the outer circumferential surface of the rubber member from its leading end to the trailing end, by the pressure-joining means which is preferably comprised of a pressure roll. Thus, the reinforcing element can be pressure-joined over its entire length to the rubber member sufficiently tightly, without any entrapment of air therebetween.
Furthermore, the reinforcing element feed means and the pressure-joining means can be displaced in the axial direction of the core at a required speed by the lateral travel means with a predetermined relation to the rotational speed of the core, so that the longitudinal direction of the reinforcing element on the outer circumferential surface of the rubber member can be set to the desired angle with reference to the equatorial line of the core. This angle can be readily changed as required, by suitably selecting the rotational speed of the core and the feeding speed of the reinforcing element.
It is preferred that the apparatus according to the invention further comprises inclination means for inclining the reinforcing element feed means and the pressure-joining means within a plane that is perpendicular to the predetermined feed direction of the reinforcing element. Such inclination means serves to positively ensure that the feeding direction of the reinforcing element can be readily aligned with the direction in which it is to be pressure-joined to the rubber member. As a result, the processes from the feeding step to the pressure-joining step of the reinforcing element can be smoothly performed without being affected by external forces acting in the twisting, tensioning or compressing direction relative to the reinforcing element. It is therefore possible to fully eliminate dislocation or deformation of the reinforcing element after it has been pressure-joined to the outer circumferential surface of the rubber member on the core.
It is preferred that the apparatus according to the present invention further comprises auxiliary feed means for assisting the reinforcing element feed means, in order to positively and smoothly feed the reinforcing element to the outer circumferential surface of the rubber member synchronously with the rotation of the core, and under the operation of this auxiliary feeding means.
It is also preferred that the apparatus according to the present invention further comprises drive means, e.g., a cylinder, for advancing and retracting the pressure-joining means relative to the outer circumferential surface of the core. With such drive means, the pressure-joining means can be advanced to urge the reinforcing element against the rubber member with a required force during the operation of the pressure-joining means, and the pressure-joining means can be retracted and separated from the outer circumferential surface of the core when the pressure-joining means is out of operation.
It is also preferred that the apparatus according to the present invention further comprises at least one of (i) cutter means for cutting a continuous strip of reinforcing material into the reinforcing elements having a predetermined length, (ii) drawer means for drawing out the continuous strip of the reinforcing material from a feed roll toward the cutter means, and (iii) correction means for eliminating a deformation tendency, such as a curling tendency, of the continuous strip of the reinforcing material as it has been drawn out of the feed roll by the drawer means.